The present invention relates to a method and apparatus for providing reference laser beams and, more particularly, to such a method and apparatus in which two such beams simultaneously define a reference line and an orthoganal reference plane.
Laser beam systems have been employed in numerous surveying and construction applications. In one such system a laser beam projector provides a rotating laser beam which initially establishes a reference plane. In use, the projector may, for example, be mounted at the desired height of a hanging ceiling in a building under construction. The beam is rotated in a horizontal plane to assist the workers in determining the proper height for the ceiling throughout the room. The rotating laser beam provides a continuous, visible plane of light that creates a constant horizontal benchmark of elevation over the entire work area. Additionally, it allows the workers to check for low duct work, sprinklers, and other obstructions before setting the support grid for the ceiling. Such a horizontal reference plane is also advantageous in constructing raised access flooring.
Typically, the laser projector can be positioned to provide a vertical reference plane of light, or a plane of light in other orientations. A laser projector of this type can be used for laying out overhead drop walls and bulkheads, and in other construction operations. Other laser projectors of a type producing a stationary reference laser beam have been used to provide a plumb line of light as a visible reference beam for plumbing elevator shafts, highrise vertical control, and slip forming.
U.S. Pat. No. 4,062,634, issued Dec. 13, 1977, to Rando et al; U.S. Pat. No. 4,035,085, issued July 12, 1977, to Ramsay; and U.S. Pat. No. 4,031,629, issued June 28, 1977, to Paluck, all disclose rotating laser beam devices. In each device, a generally horizontal rotating laser beam is produced by projecting a primary laser beam generally upward and then deflecting the beam by 90.degree. within a pentaprism or penta-mirror assembly. The pentaprism assembly is rotated about a vertical axis to cause the horizontal beam to rotate. In the past, some laser projectors have included a removable pentaprism assembly. With such a device, the plane defined by the rotating beam could be aligned with a building structure, for example such as a wall, and the pentaprism assembly could thereafter be removed to produce a reference line normal to the wall. While such a laser projector is exceptionally useful, removal of the pentaprism assembly is somewhat cumbersome, and produces the risk that the alignment of the projector may be disturbed slightly during this operation, resulting in inaccuracies.
It is seen, therefore, that there is a need for a laser projector device which produces a stationary reference beam and a rotating reference beam perpendicular thereto, in which pentaprism assembly removal is not required.